Cyclopolycondensation. XII. Polymerization mechanism of polybenzoxazinones in polyphosphoric acid medium

Abstract

The polymerization mechanism of polyphosphoric acid (PPA) solution polymerization of an aromatic diaminodicarboxylic acid with aromatic dicarboxylic acid derivatives was studied. By means of NMR methods, the initiation process for the polymerization of polybenzoxazinone in PPA medium was elucidated. The NMR spectra of a series of compounds were taken, and the salt formation of amino groups of monomer with PPA and the equilibrium between the salt and the free amino group were determined. It was established that the polymerization proceeded through the formation of phosphorylated intermediates to give the salt of amino groups of monomer with PPA. In the second step, the amine–PPA salt dissociates into the free amino group and PPA at the polymerization temperature above 140°C. Polymerization proceeds through the attack of “free” amino on phosphorylated carbonyl compounds to form polyamide acid of high molecular weight, and on subsequently being heated in PPA at higher temperatures, it undergoes an intramolecular cyclodehydration along the polymer chain to form polybenzoxazinones.

One-pot synthesis of 2-substituted 4H-3,1-benzoxazin-4-one derivatives under mild conditions using iminium cation from cyanuric chloride/dimethylformamide as a cyclizing agent

“…The benzoxazin-4-one ring is formed from intermediate formula 1 and cyclizing agents, such as acetic anhydride [6-9], polyphosphoric acid [10], sulfuric acid [11], and pyridine [12], which can convert the OH of the carboxylic acid group into a good living group W to form the benzoxazin-4-one ring (Scheme 2). …”

Microwave Assisted Synthesis of 2,2'-Arylene-substituted Bis(4H-3,1-Benzoxazin-4-one) Derivatives Using the Complex Cyanuric Chloride/N,N-Dimethylformamide

“…The most reported methods for synthesis of 2-substituted-4 H -3,1-benzoxazin-4-one derivatives are those based on preparation of an acid-amide intermediate that is cyclized by various cyclizing agents such as acetic anhydride [ 6 , 7 ], polyphosphoric acid [ 8 ] triphenyl phosphite, pyridine [ 9 ], and cyanuric chloride [ 10 , 11 ]. Formation of the acid-amide intermediate is a key step of these methods.…”

Preparation and properties of a new aromatic polyamide with an ethoxycarbonyl pendant group: Poly(4,4?-diamino-2?-ethoxycarbonyl-benzanilide terephthalamide)

“…In recent years, many thermally stable heterocyclic polymers have been reported [7][8][9][10][11][12][13][14][15][16][17][18] with the aim of overcoming the problems involved in processing PPTA. The polymer containing a benzoxazinone unit in the backbone chain is one of them and is known to have remarkable thermal stability.…”

“…The polymer containing a benzoxazinone unit in the backbone chain is one of them and is known to have remarkable thermal stability. Polybenzoxazinones 12,19 can be prepared by the reaction of suitable aromatic diaminodicarboxylic acids with aromatic dicarboxylic acid halides in polyphosphoric acid at a high tempera-ture or in dimethylacetamide (DMAc) at a low temperature.…”